The present invention relates to biomedical electrodes, that is electrodes which can be attached to the skin of a patient to establish an electrical connection between the skin and an electromedical monitoring/diagnostic/therapeutic system. The invention relates more especially, but not exclusively, to ECG electrodes for use in a part of a system for monitoring and/or diagnosing cardiac function and is likewise applicable to electrodes for use in electroencephalograph (EEG) systems.
ECG monitoring systems are well known and are used in a variety of health care situations. Such systems require the use of electrodes which are attached to the skin, at selected points of the body, to enable electrical signals (indicative of cardiac function) to be fed to an electrocardiograph. The electrodes, which are conventionally attached to the skin by an adhesive, are required to make good electrical contact with the skin and to be constructed to permit the easy attachment of electrical leads from the electrocardiograph. It is also desirable that the electrodes should be easy to remove from the protective liner material with which they are normally provided and from the skin of a patient, after use, without leaving any adhesive or other residues.
One known type of ECG electrode comprises a connector stud having a head portion to which electrical leads can be attached, and an electrode plate through which contact is made to the skin. The stud is located in a patch of backing material, with the electrode plate positioned on one side of the material and the head portion on the other. The side of the backing material on which the electrode plate is positioned is coated with an adhesive. enabling the ECG electrode to be securely attached to the skin and an electrical contact to be formed between the skin and the electrode plate. To improve the electrical connection between the skin and the electrode plate. the latter may, for example, be coated with a layer of an ionically-conductive paste, cream or gel, or covered with a layer of sponge material in which an ionically-conductive gel is embedded.
Connector studs which are formed in two parts, designed to snap together, are known. One part of the stud provides the electrode plate and the other part provides the head portion and, during the process of assembling the electrode, the two parts are located on opposite sides of the backing material and snapped together, thereby clamping the backing material between them. The connector stud is thus well anchored in the backing material so that the likelihood of it separating from the backing material when the electrode is in use is comparatively low. However, the two-part construction of the stud increases the complexity of the assembly process.
Biomedical electrodes with one-piece connector studs are also known. U.S. Pat. No. 4 352 359, for example, describes an electrode in which the connector stud is a one-piece stud, the head portion of which is located in a punched aperture in a patch of adhesive tape. The adhesive tape overlies the upper surface of the electrode stud and aids in holding the electrode securely to the skin of a patient. In another known electrode which employs a one-piece stud, the backing material is a comparatively thick foam material and an integral flange is provided in the stud at a distance from the electrode plate so that it will overlie the upper surface of the backing material. Additional shaping in the form of a smaller flange is provided on the stud between the flange and the electrode plate. The stud is located in a punched aperture in the backing material with the additional shaping on the stud thus being located within the aperture.
The use of one-piece connector studs reduces the number of components required to assemble a biomedical electrode but can increase the likelihood of the stud separating from the backing material, particularly when electrical leads are being attached to the stud. Alternatively, if the connector stud is shaped so that it is less likely to separate from the backing material, the insertion of the stud into the backing material during the assembly process can become more difficult.
U.S. Pat. No. 4 640 289 describes a biomedical electrode with a one-piece terminal member located in a punched aperture in a piece of adhesive, in which a retainer sheet is provided to prevent the terminal member separating from the remainder of the electrode. An automated method for producing the electrode is also described. The adhesive surface of the electrode is protected by a release liner and, to facilitate removal of the electrode from the release liner and, after use, from the skin of the patient, the electrode is provided with a tab formed in a margin of the adhesive tape.
U.S. Pat. Nos. 3,841,312 and 4,117,846 describe biomedical electrodes in which a separate ring or washer is employed to ensure that the connector stud is well anchored in a backing material.
The problem with which the present invention is concerned is that of enabling biomedical electrodes to be produced more simply and in a less costly manner without adversely affecting their reliability and convenience when in use.
The present invention provides a biomedical electrode comprising a backing material coated on one side with a pressure-sensitive adhesive and having a non-adhesive margin to facilitate the handling of the electrode; a connector stud located in the backing material, the stud having an electrode plate located on one side of the backing material for electrical connection to the skin of a patient and, on the other side of the backing material, a head portion to which an electrical connector can be attached; a strip of ionically-conductive adhesive extending, generally parallel to the non-adhesive margin, across the adhesive-coated side of the backing material and over the electrode plate of the stud; and a parallel strip of scrim material located at the interface of the ionically-conductive and pressure-sensitive adhesive; the strip of scrim material being displaced, relative to the electrode plate of the stud, towards the non-adhesive margin of the backing material and the edges of both strips nearest to the non-adhesive margin being positioned to one side of the electrode plate.
In one embodiment, the connector stud is one piece. In another embodiment, the connector stud comprises two pieces.
The invention further provides a biomedical electrode comprising a backing material coated on one side with a pressure-sensitive adhesive and having an adhesive-free margin to facilitate the handling of the electrode; a connector stud located in the backing material, the stud having an electrode plate located on one side of the backing material for electrical connection to the skin of the patient and, on the other side of the backing material, a head portion to which an electrical connector can be attached; and a strip of ionically-conductive adhesive extending across the adhesive-coated side of the backing material and over the electrode plate.
The present invention also provides a biomedical electrode comprising a backing material securable by an adhesive to the skin of a patient, and a connector stud located in a pierced opening in the backing material, the stud having an electrode plate located on one side of the backing material for electrical connection to the skin of the patient and, on the other side of the material, a head portion to which an electrical connector can be attached.
A method of manufacturing a biomedical electrode, comprising the steps of providing a connector stud comprising an electrode plate for electrical connection to the skin of a patient and a head portion; and inserting the connector stud into a pierced opening in a backing material, to locate the stud in the backing material with the electrode plate and the head portion on opposite sides of the material.
The present invention also provides a method of manufacturing a biomedical electrode, comprising the steps of forming an opening in a backing material; inserting a tubular member through the opening from one side of the backing material; providing a connector stud comprising an electrode plate for electrical connection to the skin of a patient, and a head portion; locating the stud, head portion first, in the end of the tubular member from the other side of the backing material.
By way of example only, embodiments of the invention will be described with reference to the accompanying drawings, in which: